It boggled my mind that Seaborn doesn't provide anything like this out of the box.
Still, it was pretty easy to tweak the source code to get what you wanted.
The following code, with the function "percentageplot(x, hue, data)" works just like sns.countplot, but norms each bar per group (i.e. divides each green bar's value by the sum of all green bars)
In effect, it turns this (hard to interpret because different N of Apple vs. Android):
sns.countplot
into this (Normed so that bars reflect proportion of total for Apple, vs Android):
Percentageplot
Hope this helps!!
from seaborn.categorical import _CategoricalPlotter, remove_na
import matplotlib as mpl
class _CategoricalStatPlotter(_CategoricalPlotter):
@property
def nested_width(self):
"""A float with the width of plot elements when hue nesting is used."""
return self.width / len(self.hue_names)
def estimate_statistic(self, estimator, ci, n_boot):
if self.hue_names is None:
statistic = []
confint = []
else:
statistic = [[] for _ in self.plot_data]
confint = [[] for _ in self.plot_data]
for i, group_data in enumerate(self.plot_data):
# Option 1: we have a single layer of grouping
# --------------------------------------------
if self.plot_hues is None:
if self.plot_units is None:
stat_data = remove_na(group_data)
unit_data = None
else:
unit_data = self.plot_units[i]
have = pd.notnull(np.c_[group_data, unit_data]).all(axis=1)
stat_data = group_data[have]
unit_data = unit_data[have]
# Estimate a statistic from the vector of data
if not stat_data.size:
statistic.append(np.nan)
else:
statistic.append(estimator(stat_data, len(np.concatenate(self.plot_data))))
# Get a confidence interval for this estimate
if ci is not None:
if stat_data.size < 2:
confint.append([np.nan, np.nan])
continue
boots = bootstrap(stat_data, func=estimator,
n_boot=n_boot,
units=unit_data)
confint.append(utils.ci(boots, ci))
# Option 2: we are grouping by a hue layer
# ----------------------------------------
else:
for j, hue_level in enumerate(self.hue_names):
if not self.plot_hues[i].size:
statistic[i].append(np.nan)
if ci is not None:
confint[i].append((np.nan, np.nan))
continue
hue_mask = self.plot_hues[i] == hue_level
group_total_n = (np.concatenate(self.plot_hues) == hue_level).sum()
if self.plot_units is None:
stat_data = remove_na(group_data[hue_mask])
unit_data = None
else:
group_units = self.plot_units[i]
have = pd.notnull(
np.c_[group_data, group_units]
).all(axis=1)
stat_data = group_data[hue_mask & have]
unit_data = group_units[hue_mask & have]
# Estimate a statistic from the vector of data
if not stat_data.size:
statistic[i].append(np.nan)
else:
statistic[i].append(estimator(stat_data, group_total_n))
# Get a confidence interval for this estimate
if ci is not None:
if stat_data.size < 2:
confint[i].append([np.nan, np.nan])
continue
boots = bootstrap(stat_data, func=estimator,
n_boot=n_boot,
units=unit_data)
confint[i].append(utils.ci(boots, ci))
# Save the resulting values for plotting
self.statistic = np.array(statistic)
self.confint = np.array(confint)
# Rename the value label to reflect the estimation
if self.value_label is not None:
self.value_label = "{}({})".format(estimator.__name__,
self.value_label)
def draw_confints(self, ax, at_group, confint, colors,
errwidth=None, capsize=None, **kws):
if errwidth is not None:
kws.setdefault("lw", errwidth)
else:
kws.setdefault("lw", mpl.rcParams["lines.linewidth"] * 1.8)
for at, (ci_low, ci_high), color in zip(at_group,
confint,
colors):
if self.orient == "v":
ax.plot([at, at], [ci_low, ci_high], color=color, **kws)
if capsize is not None:
ax.plot([at - capsize / 2, at + capsize / 2],
[ci_low, ci_low], color=color, **kws)
ax.plot([at - capsize / 2, at + capsize / 2],
[ci_high, ci_high], color=color, **kws)
else:
ax.plot([ci_low, ci_high], [at, at], color=color, **kws)
if capsize is not None:
ax.plot([ci_low, ci_low],
[at - capsize / 2, at + capsize / 2],
color=color, **kws)
ax.plot([ci_high, ci_high],
[at - capsize / 2, at + capsize / 2],
color=color, **kws)
class _BarPlotter(_CategoricalStatPlotter):
"""Show point estimates and confidence intervals with bars."""
def __init__(self, x, y, hue, data, order, hue_order,
estimator, ci, n_boot, units,
orient, color, palette, saturation, errcolor, errwidth=None,
capsize=None):
"""Initialize the plotter."""
self.establish_variables(x, y, hue, data, orient,
order, hue_order, units)
self.establish_colors(color, palette, saturation)
self.estimate_statistic(estimator, ci, n_boot)
self.errcolor = errcolor
self.errwidth = errwidth
self.capsize = capsize
def draw_bars(self, ax, kws):
"""Draw the bars onto `ax`."""
# Get the right matplotlib function depending on the orientation
barfunc = ax.bar if self.orient == "v" else ax.barh
barpos = np.arange(len(self.statistic))
if self.plot_hues is None:
# Draw the bars
barfunc(barpos, self.statistic, self.width,
color=self.colors, align="center", **kws)
# Draw the confidence intervals
errcolors = [self.errcolor] * len(barpos)
self.draw_confints(ax,
barpos,
self.confint,
errcolors,
self.errwidth,
self.capsize)
else:
for j, hue_level in enumerate(self.hue_names):
# Draw the bars
offpos = barpos + self.hue_offsets[j]
barfunc(offpos, self.statistic[:, j], self.nested_width,
color=self.colors[j], align="center",
label=hue_level, **kws)
# Draw the confidence intervals
if self.confint.size:
confint = self.confint[:, j]
errcolors = [self.errcolor] * len(offpos)
self.draw_confints(ax,
offpos,
confint,
errcolors,
self.errwidth,
self.capsize)
def plot(self, ax, bar_kws):
"""Make the plot."""
self.draw_bars(ax, bar_kws)
self.annotate_axes(ax)
if self.orient == "h":
ax.invert_yaxis()
def percentageplot(x=None, y=None, hue=None, data=None, order=None, hue_order=None,
orient=None, color=None, palette=None, saturation=.75,
ax=None, **kwargs):
# Estimator calculates required statistic (proportion)
estimator = lambda x, y: (float(len(x))/y)*100
ci = None
n_boot = 0
units = None
errcolor = None
if x is None and y is not None:
orient = "h"
x = y
elif y is None and x is not None:
orient = "v"
y = x
elif x is not None and y is not None:
raise TypeError("Cannot pass values for both `x` and `y`")
else:
raise TypeError("Must pass values for either `x` or `y`")
plotter = _BarPlotter(x, y, hue, data, order, hue_order,
estimator, ci, n_boot, units,
orient, color, palette, saturation,
errcolor)
plotter.value_label = "Percentage"
if ax is None:
ax = plt.gca()
plotter.plot(ax, kwargs)
return ax
